EQUILIBRIUM SWELLING PROPERTIES OF POLYAMPHOLYTIC HYDROGELS

The role of counter ions and ion dissociation in establishing the equi librium swelling of balanced and unbalanced polyampholytic hydrogels h as been investigated experimentally and theoretically. The swelling de pendence on both the net charge offset and the external bath salt conc entration has been examined using an acrylamide based polyampholytic h ydrogels. By careful consideration of the swelling kinetics, we illust rate the effects of ion dissociation equilibria and counter ion shield ing in polyampholytic hydrogels near their balance point where both po lyelectrolyte and polyampholyte effects are present. The theory consid ers a Flory type swelling model where the Coulombic interactions betwe en fixed ions in the hydrogel resemble those of an ionic solid with a Debye screening factor. Theoretical predictions from this model are in qualitative agreement with our experimental results. (C) 1996 America n Institute of Physics.